DESCRIPTION: Misfolded proteins are found in many inherited diseases, which collectively are called protein conformational disorders (PCDs). Most often the mutant proteins are retained in the cell, either in the endoplasmic reticulum (ER), in cytoplasmic inclusions and possibly aggresomes. The misfolded polypeptides are found associated with various chaperones including the two most abundant - BiP, an ER chaperone, and Hsp70, a cytosolic chaperone. Our previous studies clearly demonstrated that the clinically common P23H opsin mutant associated with autosomal dominant retinitis pigmentosa (ADRP) is misfolded and retained in the cell. Gene therapy approaches have been used to retard the rate of retinal degeneration in the P23H rat by using AAV vectors designed to deliver growth factors or ribozymes to rod photoreceptors. Recently we have generated a new transgenic mouse that is genetically similar to the human disease. Additionally, we have constructed AAV or are currently constructing vectors that express either BiP or hsp70 in photoreceptors or express small peptides known to specifically bind Hsp70 or BiP. Using these animals and vectors we will test two mechanistically alternative hypotheses: either over-expression or blocking the activity of hsp70 or BiP will serve to correctly process misfolded P23H opsin thereby retarding the rate of retinal degeneration. If either approach is successful in slowing the rate of retinal degeneration in our human P23H transgenic mouse, functional testing will be broadened to other animal models of misfolded opsins, including the T17M transgenic mouse and the T4R opsin dog (independent funding would be sought to support these later aims). This would validate the generality of "folding modulation therapy" and suggest its applicability to other PCDs. In this sense, this proposal is not just testing a hypothesis regarding a narrowly specific retinal disease, but rather is attempting to lay the groundwork for a therapy with broad utility. Thus, although the proposal is "risky" in that there is no guarantee of therapy, the "payoff" is potentially large.